1. Field of the Invention
The present invention relates to a method for forming a gate electrode of a semiconductor device, and more particularly, the present invention relates to a method for forming a gate electrode of a semiconductor device, which prevents properties of a semiconductor device from being degraded due to the fact that metal having a high melting point and used as a gate electrode when implementing a thermal treating process of a gate oxide film under an oxidizing atmosphere for improving the film""s quality thereof, is oxidized.
2. Description of the Related Art
Generally, a doped polysilicon is widely used as a gate electrode of a semiconductor device.
While a gate electrode formed using a polysilicon has an advantage of its processes being stable due to a high specific resistance of the polysilicon, design rule is decreased, thereby it is difficult to increase an operating speed of a semiconductor device.
To cope with this problem, it is disclosed in the art that high melting point metal such as tungsten having a low specific resistance be used to form a gate electrode.
In light of the above statements, while not shown in a drawing, a method for forming a gate electrode of a semiconductor device according to the conventional art will be described hereinbelow in connection with the case that tungsten is used as the high melting point metal.
First, a gate oxide film is formed on a semiconductor substrate to have a constant thickness. Then, a first polysilicon film, a tungsten film for a gate electrode and a mask oxide film are formed on a resultant structure.
Then, by etching a resultant structure using a gate electrode mask, a gate electrode is patterned. Thereafter, an oxidation preventing film spacer is formed on a side wall of the gate electrode using a second polysilicon film.
However, when a gate reoxide film is formed by an oxidizing process to compensate a gate oxide film which is etched by ion-implanting and etching processes, if a degree of oxidation is not properly controlled, the tungsten film can be oxidized.
In other words, in the method for forming a gate electrode of a semiconductor device according to the conventional art, as mentioned above, in the case that tungsten being metal having a high melting point is used as a gate electrode, the tungsten film can be oxidized when the gate reoxide film is formed by the oxidizing process, whereby properties of a semiconductor device can be degraded and according to this, it is difficult to accomplish high integration and high speed of the semiconductor device.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an objective of the present invention is to provide a method for forming a gate electrode of a semiconductor device, in which an oxidation preventing film is formed by a stack structure of a polysilicon film and a nitride film, thereby improving film quality of a gate oxide film on a semiconductor device which is damaged when implementing a patterning process of a gate electrode.
Another objective of the present invention is to provide a method for forming a gate electrode of a semiconductor device, which prevents properties of a gate electrode formed by metal having a high melting point from being degraded when thermally treating a gate oxide film under an oxidizing atmosphere for forming a gate reoxide film to be used in a lightly-doped drain (LDD) ion-implanting process, thereby enabling a semiconductor device to be highly integrated.
In accordance with one aspect, the present invention provides a method for forming a gate electrode of a semiconductor device, comprising the steps of: stacking a gate oxide film, a doped first silicon film, a diffusion preventing film, a metal film having a high melting point for a gate electrode and a mask insulating film on a semiconductor substrate; forming a gate electrode by patterning a resultant stack structure; forming a second silicon film on an entire surface of a resultant structure; forming an oxidation preventing film on an entire surface of a resultant structure; forming a spacer on a side wall of the gate electrode by anisotrophically etching the oxidation preventing film and the second silicon film; and forming a gate reoxide film by oxidizing the semiconductor substrate.
In accordance with another aspect, the present invention provides a method for forming a gate electrode of a semiconductor device, comprising the steps of: stacking a gate oxide film, a doped first polysilicon film, a diffusion preventing film, a tungsten film and a mask insulating film on a semiconductor substrate; forming a gate electrode by patterning a resultant stack structure; forming a second polysilicon film on an entire surface of resultant structure; forming an nitride film for an oxidation preventing film on an entire surface of a resultant structure; forming a spacer on a side wall of the gate electrode by anisotrophically etching the nitride film and the polysilicon film; and forming a gate reoxide film on the semiconductor substrate by oxidizing a lower portion of the second polysilicon film and the semiconductor substrate.